1. Field of the Invention
The present invention concerns a curable liquid-form composition, the cured product of said composition, and an electronic part. More specifically, the present invention concerns (a) a curable liquid-form composition which has superior working characteristics in liquid form prior to being cured, and which when cured forms a cured product which has superior pliability, initial bonding characteristics and bonding durability in spite of the fact that the hardness of said cured product is relatively high; (b) a cured product which has superior pliability in spite of the fact that the hardness of said cured product is relatively high; and (c) an electronic part with superior reliability which is covered by the cured product of the abovementioned composition.
2. Description of the Related Art
Curable liquid-form organopolysiloxane compositions have superior working characteristics in the liquid state prior to being cured; furthermore, when cured, such compositions form cured products which have superior electrical characteristics such as volume resistivity, insulation breakdown strength and dielectric constant, etc. Accordingly, such compositions can be favorably used as covering agents such as protective agents and sealing agents, etc., for electronic parts. However, although the cured products of such compositions have a relatively high hardness and high pliability, these cured products have a low mechanical strength. Accordingly, electronic parts which are covered by such cured products are easily damaged by external stress. Generally, the cured products obtained from such compositions can be endowed with mechanical strength and a high hardness by mixing large quantities of inorganic fillers or organic filers with the compositions. However, the compositions obtained as a result have poor fluidity in the liquid state, and show a conspicuous drop in working characteristics. Furthermore, such compositions also show a drop in bonding characteristics with respect to various types of materials. Moreover, electronic parts which are covered by the cured products of such compositions do not show a very great improvement in reliability (in terms of resistance to moisture, etc.).
Curable liquid-form organic resin compositions, such as, for example, curable liquid-form epoxy resin compositions, curable liquid-form polyimide resin compositions and curable liquid-form phenol resin compositions, also have superior working characteristics in the liquid state prior to being cured, and can therefore penetrate into minute areas of electronic parts. The cured products of such compositions have good electrical properties and can, therefore, used as covering agents for electronic parts. However, such cured products have a high hardness, poor pliability and a large mechanical strength. As a result electronic parts which are covered by such cured products are easily damaged by internal stresses, and crag tends to occur in the cured products themselves. Accordingly, numerous methods have been proposed to reduce the hardness and increase the pliability of cured products obtained from such compositions without causing a drop in the mechanical strength of such cured products. One such method involves mixing large quantities of fine particles of a cured organopolysiloxane with the compositions (see Japanese Patent Application Kokai No. 61-225253, Japanese Patent Application Kokai No. 62-232460, Japanese Patent Application Kokai No. 1-221457 and Japanese Patent Application Kokai No. 2-41353). However, such compositions show poor fluidity and a conspicuous deterioration in working characteristics. Furthermore, such compositions exhibit decreased adhesion to various types of materials. Moreover, electronic parts which are covered by the cured products of such compositions do not show a very great improvement in reliability (in terms of resistance to moisture, etc.).
In order to solve such problems, curable liquid-form compositions which consist of a curable liquid-form organopolysiloxane composition and a curable liquid-form organic resin composition, and in which the organopolysiloxane composition is contained as liquid particles in the organic resin composition, have been proposed (see Japanese Patent Application Kokai 54-54168, Japanese Patent Application Kokai No. 55-3412, Japanese Patent Application Kokai No. 64-38418 and Japanese Patent Application Kokai No. 5-295233). However, although such curable liquid-form compositions have superior working characteristics in the liquid state prior to being cured, the curing of these compositions produces cured products in which fine particles of a cured organopolysiloxane are contained in a matrix consisting of a cured organic resin. As a result these cured products still have a high hardness, poor pliability and a high mechanical strength. Accordingly, in the case of electronic parts covered by means of such cured products, the problems of susceptibility to damage caused by internal stresses and susceptibility of the cured products themselves to cracking have not been sufficiently solved Furthermore, although these cured products show good initial bonding characteristics with respect to various types of materials, the bonding durability of such cured products is unsatisfactory. In addition, electronic parts which are covered by the cured products of such compositions do not show satisfactory reliability.
It is an object of the present invention is to provide (a) a curable liquid-form composition which has superior working characteristics in liquid form prior to being cured, and which when cured forms a cured product which has superior pliability, initial bonding characteristics and bonding durability in spite of the fact that the hardness of said cured product is relatively high, (b) a cured product which has superior pliability in spite of the fist tat the hardness of said cured product is relatively high, and (c) an electronic part with superior reliability which is covered by the cured product of the abovementioned composition.